diff --git a/.changeset/tidy-boxd-cancellation.md b/.changeset/tidy-boxd-cancellation.md
new file mode 100644
index 0000000000..7e1d0b553f
--- /dev/null
+++ b/.changeset/tidy-boxd-cancellation.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/ai-sandbox-boxd': patch
+---
+
+Delete newly created machines when create or snapshot restore is aborted during readiness or workspace setup.
diff --git a/docs/sandbox/providers.md b/docs/sandbox/providers.md
index b968c77ed7..86a6f330a1 100644
--- a/docs/sandbox/providers.md
+++ b/docs/sandbox/providers.md
@@ -436,6 +436,9 @@ const boxd = boxdSandbox({
   100 GB disk.
 - **Working directory:** the portable root `/workspace` maps to
   `/home/boxd/workspace`. Override with `workdir`.
+- **Cancellation:** if you abort create or snapshot restore during startup,
+  the provider tries to delete the new machine after the current SDK call
+  finishes.
 - **Processes:** `spawn()` opens a streaming exec with separate stdout and
   stderr and a writable stdin. `kill()` signals the process group inside the
   machine and verifies that it is gone, so `killableProcesses` is measured,
diff --git a/packages/ai-sandbox-boxd/src/provider.ts b/packages/ai-sandbox-boxd/src/provider.ts
index 8f2bbc10db..e86c68a7f2 100644
--- a/packages/ai-sandbox-boxd/src/provider.ts
+++ b/packages/ai-sandbox-boxd/src/provider.ts
@@ -154,12 +154,14 @@ class BoxdProvider implements SandboxProvider {
     try {
       input.signal?.throwIfAborted()
       const ready = await this.client.machines.waitUntilReady(machine.id)
+      input.signal?.throwIfAborted()
       const handle = this.handle(ready, input.env)
       // From `/`: the workdir does not exist yet, and every handle exec `cd`s
       // into its cwd first.
       const mkdir = await handle.process.exec(`mkdir -p ${q(this.workdir)}`, {
         cwd: '/',
       })
+      input.signal?.throwIfAborted()
       if (mkdir.exitCode !== 0) {
         throw new Error(
           `boxd: failed to create workspace directory "${this.workdir}" (exit ${mkdir.exitCode}): ${mkdir.stderr.trim()}`,
diff --git a/packages/ai-sandbox-boxd/tests/provider.test.ts b/packages/ai-sandbox-boxd/tests/provider.test.ts
index daaa0793a2..32904757c8 100644
--- a/packages/ai-sandbox-boxd/tests/provider.test.ts
+++ b/packages/ai-sandbox-boxd/tests/provider.test.ts
@@ -70,6 +70,38 @@ afterEach(() => {
   delete process.env.BOXD_ORG
 })
 
+describe('boxdSandbox provider: cancellation during adoption', () => {
+  it('rejects create aborted during readiness and deletes its machine', async () => {
+    const controller = new AbortController()
+    const reason = new Error('adoption cancelled')
+    machines.waitUntilReady.mockImplementation(async () => {
+      controller.abort(reason)
+      return machine()
+    })
+    await expect(
+      boxdSandbox({ apiKey: 'k' }).create({ signal: controller.signal }),
+    ).rejects.toBe(reason)
+    expect(machines.delete).toHaveBeenCalledExactlyOnceWith('vm-1')
+    expect(machines.exec).not.toHaveBeenCalled()
+  })
+
+  it('rejects restore aborted during workspace setup and deletes its machine', async () => {
+    const controller = new AbortController()
+    const reason = new Error('adoption cancelled')
+    machines.exec.mockImplementation(async () => {
+      controller.abort(reason)
+      return ok
+    })
+    await expect(
+      boxdSandbox({ apiKey: 'k' }).restoreSnapshot!({
+        snapshotId: 'saved-workspace',
+        signal: controller.signal,
+      }),
+    ).rejects.toBe(reason)
+    expect(machines.delete).toHaveBeenCalledExactlyOnceWith('vm-1')
+  })
+})
+
 describe('boxdSandbox provider: create', () => {
   it('creates an isolated machine named after the deterministic id, in the org, at the requested size', async () => {
     const handle = await boxdSandbox({
diff --git a/testing/e2e/tests/sandbox-boxd-startup-cancellation.spec.ts b/testing/e2e/tests/sandbox-boxd-startup-cancellation.spec.ts
new file mode 100644
index 0000000000..650cde83fe
--- /dev/null
+++ b/testing/e2e/tests/sandbox-boxd-startup-cancellation.spec.ts
@@ -0,0 +1,47 @@
+import { spawnSync } from 'node:child_process'
+import { expect, test } from '@playwright/test'
+
+test('boxd create cleans up an aborted startup in the built package', () => {
+  const result = spawnSync(
+    process.execPath,
+    [
+      '--input-type=module',
+      '--eval',
+      `
+        import assert from 'node:assert/strict'
+        import { createRequire } from 'node:module'
+        import { boxdSandbox } from './packages/ai-sandbox-boxd/dist/esm/index.js'
+
+        const require = createRequire(new URL('./packages/ai-sandbox-boxd/package.json', import.meta.url))
+        const { Boxd } = await import(require.resolve('@boxd-sh/sdk'))
+        const client = new Boxd({ token: 'unused-test-token' })
+        const machines = Object.getPrototypeOf(client.machines)
+        const machine = { id: 'vm-1', name: 'm', status: 'running', access: { url: 'https://m.boxd.sh' } }
+
+        const controller = new AbortController()
+        const reason = new Error('startup cancelled')
+        const deleted = []
+        machines.create = async () => machine
+        machines.waitUntilReady = async () => {
+          controller.abort(reason)
+          return machine
+        }
+        machines.delete = async (id) => { deleted.push(id) }
+        const result = boxdSandbox({ apiKey: 'unused-test-key' }).create({ signal: controller.signal })
+        await assert.rejects(result, (error) => error === reason)
+        assert.deepEqual(deleted, ['vm-1'])
+        await client.close()
+        console.log('create cancelled; machine deleted')
+      `,
+    ],
+    {
+      cwd: new URL('../../../', import.meta.url),
+      encoding: 'utf8',
+      timeout: 20_000,
+    },
+  )
+
+  expect(result.error).toBeUndefined()
+  expect(result.status, result.stderr).toBe(0)
+  expect(result.stdout).toContain('create cancelled; machine deleted')
+})